Improve the OOME fragmentation message.

Change-Id: I390d3622f8d572ec7e34ea6dff9e1e0936e81ac1
diff --git a/runtime/gc/space/malloc_space.h b/runtime/gc/space/malloc_space.h
index d24016c..6f49fbf 100644
--- a/runtime/gc/space/malloc_space.h
+++ b/runtime/gc/space/malloc_space.h
@@ -19,6 +19,7 @@
 
 #include "space.h"
 
+#include <iostream>
 #include <valgrind.h>
 #include <memcheck/memcheck.h>
 
@@ -132,6 +133,8 @@
     return can_move_objects_;
   }
 
+  virtual void LogFragmentationAllocFailure(std::ostream& os, size_t failed_alloc_bytes) = 0;
+
  protected:
   MallocSpace(const std::string& name, MemMap* mem_map, byte* begin, byte* end,
               byte* limit, size_t growth_limit, bool create_bitmaps, bool can_move_objects,